A Viburnum With Some Teeth

Viburnum dentatum

I’ve been bicycling to work on paths that are often separated from the road by a vegetated buffer that is 20 or 30 feet wide. Over the past three weeks I have noticed a flowering shrub with white corymbs and broadly ovate toothed leaves. The habit is a cluster of arched trunks. When the apical bud is broken off other buds along the branch send new branches straight up, giving rise to the common name for this viburnum, arrowwood.

The real name for this shrub is Viburnum dentatum. It is one of several viburnum species distributed through southern New England. This species seems to be especially common in the sandy plains of down-island Martha’s Vineyard. Indeed, at least one of the plant guides notes its preference for coastal areas. It likes well drained soils, but tolerates a wide variety of settings and established plants are somewhat drought tolerant. All these characteristics will help survive the rigors of the central plain of this island, which is so dry that it was never farmed until the advent of drilled wells and large parts of it have never been farmed at all.

Space filling arrowwood as landscape shrub.

As with many easy going shrubs, this one is popular as an ornamental. It suckers like crazy around the base, so it is a good space filler and is planted around parking lots where you want to hide the lot and to prevent users from cutting through where they are not supposed to. The fact that it has attractive blossoms and berries—blue-black drupes—is simply a bonus. It does not need much maintenance although you are advised to prune it after it flowers.

Viburnums (which are part of the Caprifoliaceae family) are part of a small group of woody plants that have leaves that are oppositely arranged. The other common ones are Acer (the maples), Fraxinus (the ashes), Cornus (the dogwoods), Aesculus (the horseschestnuts and buckeyes). People used an acronym as a mnemonic to remember them all: MADCap Horse.

V. dentatum berries

Viburnums have been plagued by the viburnum leaf beetle (Pyrrhalta viburni), which is native to Europe and Asia and was introduced to Ontario, Canada in 1947. It reached Maine in 1994 and soon became a major pest throughout the northeastern U.S. V. dentatum is actually one of the species that is highly susceptible to an attack and a specimen will be killed two or three years into an infestation. There is a boom and bust pattern to the beetle populations. In spite of efforts to save landscape shrubs with sprays and removal of the egg-infested twigs, the beetles reach a point where they have reduced the local populations of viburnums to such low numbers that the larvae begin to starve. In addition, the populations of the natural predators rise along with the beetle populations. Infestations last for a few years and then it is advisable to wait several years before replanting viburnums as ornamentals.

In a 2011 article in the Vineyard Gazette that was about beetle infestations in general, Tom Clark of the Polly Hill Arboretum was quoted thusly: ““When this insect [the viburnum leaf beetle] gets here, it’s more a matter of time than anything else, it’s going to do some serious damage.” In other words, there are a lot of arrowwood viburnums along the bike paths here because the beetle has not yet crossed the seven miles of open sea to get here. In 2004 the state extension service reported that the beetle had crossed the Massachusetts/New York border and was laying waste to the Great Barrington area in the Berkshires. In 2012 the statewide report from the extension was still listing it only as a problem in the Berkshire region and it was a diminishing one.

 

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Silvery Russian Autumn

I remember “Russian olive” and “autumn olive” being used interchangeably when I was a kid, planting these exotic shrubs in our yard after purchasing them from the Department of Environmental Conservation in New York. Back in the 1970s the DEC had a program with the goal of getting the public to plant shrubs that provided food for birds. Another species we planted was the “high-bush cranberry” (Viburnum opulus var. americanum). The “olives” are not in fact related to the trees that produce actual olives and the “cranberry” is not related to the creeping woody plant that produces actual cranberries, and both species are now judged to be invasive.

E. umbellata

As it turns out the Russian olive is Elaeagnus angustifolia and the autumn olive is Elaeagnus umbellata, two different species in the same genus, both of them from Asia. As its name suggests the Russian olive has the narrower leaves and its blossoms are a yellowish color, while the autumn olive has more ovate leaves and cream colored to white flowers.

The flowers of both species are extremely aromatic. This time o] f the year if you are downwind, you are likely to smell the shrub before you see it. It is a heavy, sweet odor that reminds me of inexpensive perfume. The petals are joined into a tube with the distal ends free and flaring outward. They hang in clusters from the ends of the branches and bloom for several weeks, starting in May and continuing into June here on Martha’s Vineyard, where they are abundant.

E. angustifolia

Both E. angustifolia and E. umbellata leaves have a silvery sheen to them because of tiny scales on the surfaces. In addition to the difference in the shape of the leaves and the color of the blossoms, the scales fall off the tops of E. umbellata leaves through the growing season while the E. angustifolia leaves remain shiny.

The shrubs I have seen on Martha’s Vineyard have creamy colored flowers and are likely autumn olive. I grows in the usual places that you expect to see “volunteer” species, along roadsides, under fence lines, and in the margins of yards. Because the plant was widely distributed to be bird food, birds that ingest the fruit poop out the seeds anywhere they sit, which is often at the edges of places. I have not seen monocultural groves of the species here, which can apparently happen where it really thrives.

Native to China, Japan, and Korea, E. umbellata was introduced to the U.S. in 1830 as an ornamental, and after the 1950s was promoted for erosion control and wildlife habitat in disturbed areas.Herbivores are not known to browse on it. With the help of nitrogen-fixing nodules on its roots, it can grow in soils that are unfavorable to other species. It is also drought tolerant. Once it takes hold, it can create dense thickets that prevent other plants from germinating.

Autumnberries

A single shrub can produce 200,000 seeds. In order to get rid of a specimen, it is best to do it before it sets fruit, because the act of removing the plant can disperse the seed. It is a weedy species and will grow back more thickly after it is cut down, so it is best to remove it entirely.

Somewhat ironically, the bright red berries are growing in popularity among the forager community. They are rich in vitamins A, C, and E, and in flavonoids and lycopene. It has even been rebranded as “autumnberry” in this context. Foragers boil the berries to make jam, which kills the seeds. This, they say, kills the seeds and is a better way to prevent their spread than using herbicides. The berries of the Russian olives are yellow when young and turn red when mature, but although sweet, they are drier and mealier than autumn olive berries.

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Waxy Bells of the Laurels

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Vaccinium corymbosum

Somehow I have missed the parade of Vaccinium blooms until now. They and the closely-related Gaylussacia are ericads (laurels) that flower before and during leaf out in late April and into early May, while the larger laurels bloom later in May or into June and July and even August. The Vaccinium species—various blueberries and cranberries—and Gaylussacia—most of the huckleberries—have waxy bell-shaped flowers. The flowers of the blueberries are creamy colored with the high-bush species having tinges of pink. The local huckleberry flower tends to have little or no pink tint, although they are often described as being orange.

The cranberries (V. macrocarpon) have more specialized wetland habitat, which does exist on the island, most famously on Wampanoag land in Aquinnah, and their flowers have a different appearance. They are quite pink and have downward pointed cones of stamens and a style in front of a whorl of reflexed petals.

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Vaccinium angustifolium

Here on Martha’s Vineyard the high-bush blueberries (V. corymbosum) appear to flower first, followed by the low-bush (V. angustifolium), and then the huckleberries (G. baccata). While the huckleberries are ubiquitous on Martha’s Vineyard, the low-bush blueberries are nearly so, but the high-bush blueberries occur more  sporadically in the wild.

All the ericads are acid-soil loving plants and the dominant oak canopy assures that the low pH substrate is widespread on the island. We were walking through a Land Bank property off Middle Road recently and encountered a veritable grove of V. corymbosum that were six to eight feet high. Some of the canopy trees and understory had been removed around them, which gave them more light and they were flowering profusion as a result.

Blueberries are self-pollinating, but the berries are bigger if they are cross-pollinated. Pollination can be accomplished by either bees or the wind, but the plants have to be close together to achieve cross-pollination. V. corymbosum will not self-pollinate. It was cultivated by North American tribal peoples for thousands of years and is now the most often commercially cultivated species.

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Gaylussacia baccata

Low-bush blueberries are grown commercially in Maine, Massachusetts, and Nova Scotia, where the patches are managed wild plants. They are harvested by raking them; the “rakes” are like dust bins with tines. Using this tool is a vernacular art peculiar to the region. Outside of these areas the high-bush blueberries are picked by hand.

Blueberries are one of those crops—like almonds and oranges—that are pollinated by imported bees. Farmers bring the hives to the fields during the flowering. As they start flowering in April here and in May farther north, bumble bees are sometimes used to supplement the honey bees. Bumble bees will fly in colder weather and pollinate the flowers differently. I have seen bumble bees flying around here on Martha’s Vineyard, but as yet have not seen a honey bee.

I am still confused by the creamy color of the huckleberry flowers around here. All images that I find online are a bright reddish orange. The dwarf huckleberry (G. bigeloviana) has whitish flowers, but is supposedly a more northern plant that is said to be rare south of New Hampshire and is not recorded on Martha’s Vineyard at all. It is possible I am misidentifying some low-bush blueberries as huckleberries. That will become more clear when the leaf out is completed.

Both G. baccata and V. angustifolium growth is abetted by fire. Controlled burns are used regularly on conservation lands on this island in order to stop succession from heath to forest. In some areas here the huckleberries are almost a monoculture in the understory and the blueberries might be more common than I think. In any case, I’m looking forward to July when all of these plants bear fruit.

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Fern That Drops Its “R”s

What exactly does the “Boston” fern have to do with The Hub? (And does anyone call Boston ‘the hub’ anymore?) Nephrolepis exaltata is a subtropical plant, occurring naturally as far north as south Florida and throughout the West Indies, Mexico, Central and South America, Polynesia and Africa. It is classified as an invasive alien in South Africa, where by law it is eradicated on sight.

Wild type Nephrolepis exaltata in a Florida landscape design.

The wild type is often called a sword fern, but that common name is also given to several species of fern in the genus Polystichum. It is so named because its fronds stick nearly straight up in the air to the height of three feet. In the wild it forms thickets throughout south Florida. Nephrolepis cordifolia is invasive in south Florida, forming impenetrable thickets that have to be removed to permit native species to grow.

As a house plant the cultivars are ubiquitous. The pinnae on the fronds are alternate (some ferns are opposite), and in the wild type the sori (which hold the spores) . The gracefully arching fronds that make this fern so popular in hanging baskets and on elevated shelves are the result of a mutation that has been preserved by reproducing the plant through division. The name of the variety is ‘Bostoniensis.’

The “-ensis” suffix is common in the trivial names of plants because it means “of or from <a place>.” Sometimes the reference can be a little esoteric, as in the case of the York groundsel, a species of ragwort, Senecio eboracensis. Eboracum is the Roman name for the modern city of York in northern England. The self-pollinating ragwort grows only between a railway and a parking lot in that city.

The origin of the varietal name of N. exaltata is not definitely known. One story has it that the mutation was discovered in 1894  in a shipment of plants that was sent from Philadelphia to Boston. American botanist David Fairchild claimed that the cultivar was named by a Florida nurseryman who developed it and sent specimens to a friend in Boston.

As popular as they are, Boston ferns are non-trivial to grow, although nearly all the internet plant sites will tell you it is easy to maintain. They are in fact easier to grow indoors compared to most other ferns, most of which need to be kept in terrariums.

Although they are known to be incredibly efficient at improving indoor air (turning carbon dioxide into oxygen through photosynthesis), they are also very sensitive to indoor air pollutants, such as coal and wood smoke. They also dislike drafts.

Nephrolepis exaltata ‘Bostoniensis’ spreads via runners.

This latter quality is one particularly true of the ‘Bostoniensis’ cultivar. The species is more tolerant of the cold and was a popular Victorian house plant. The Victorians famously believed in the improving quality of fresh air and routinely opened windows in cold weather to air out their homes. They actually went so far as to make sure no vegetation grew next to the houses that might impede the flow of air.

These ferns need to be kept watered because in addition to producing oxygen they also pump water vapor into the air. The roots should never be allowed to dry out. It is necessary to mist the fronds if the humidity in your house falls below 80 percent. If grown inside it requires bright but filtered light.

“Sword ferns” growing in the wild in Florida.

If grown in a pot, it should be in standard peat-based mixture. Otherwise mix half soil-based mixture with half leaf mold. When the plant’s roots fill the pot, move it to another pot only one size larger. It will just keep growing, so when it gets to the maximum size that you want to tolerate, just trim off the outermost roots and put it back in the pot.

It can be grown outside in USDA Plant Hardiness Zones 8B through 11, roughly South Carolina to Florida on the East Coast, where natural humidity would be adequate. Although the plant will die back during the winter in the northern part of this range, it will sprout new foliage in the spring. The species (without the arching fronds) reaches two to three feet in height and spreads by runners, so it forms a thick monocultural patch wherever you plant it and needs to be thinned periodically.

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The Underwater Meadow

Eelgrass (Zostera marina on the U.S. east coast) is a flowering plant that grows submerged in salt water. In other words, it is not a “seaweed,” which are macrophytic algae. Eelgrass is descended from land plant that found a new niche by growing underwater in bays and estuaries where the bottom is shallow enough that a rooted plant can get enough sunlight to survive.

eelgrass flowersEelgrass beds on the east coast of the United States have expanded and contracted through recorded history. They are in decline in many places right now because increased development along the coast has led to nutrient loading in shallow marine environments.

Nitrogen is available in usable form in very limited amounts in the natural environment, so photosynthesizing organisms — higher plants, algae, and bacteria — are adapted to this limitation to their growth. Septic systems and fertilizers introduce relatively large amounts of nitrogen (and phosphorus) to the adjacent marine setting. Algae reacts very quickly to the elevated nitrogen levels and “blooms.” These mats of algae block the sunlight and make it difficult for eelgrass to photosynthesize.

Eelgrass has other challenges, including scouring of the seafloor by mooring chains and churning of the water column by boat propellers. Moorings are kept in place by weights and attached to the floats at the surface by chains. At lower tides the extra length of chain drags around the bottom in a circle around the weight, tearing up eelgrass by the roots. Motorboats that drive through eelgrass beds slice through the submerged and floating foliage of the plants.

These are monoecious plants — there are male and female flowers on the same plant — with long narrow leaves. The leaves are 1.2 cm wide and a meter long. The plant reproduces vegetatively via rhizomes and also when pieces of the plant break off and settle elsewhere. It also reproduces sexually by producing seeds that are dispersed by currents. As a result of the vegetative reproduction eelgrass can form extensive beds that are sometimes centuries old. It is a perennial, so the entire plant is present throughout the year.

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Seahorse in eelgrass bed

Because eelgrass beds are both extensive and present year round they have become important habitat for other life forms, including bay scallops, immature cod and mature flounder, crabs, and green algae that grow on the higher plants. Many other animals depend on eelgrass for food, including brant, isopods, and sea urchins.

In the early 1930s elevated temperatures in shallow marine environments on both the east and west coasts of the Atlantic Ocean caused an outbreak of mold that decimated eelgrass beds. In places like Buzzards Bay, Mass. the beds did not recover until the early 1960s. In Barnegat Bay, N.J. the disappearance of the eelgrass beds ends a local industry that harvested the plants to use them to insulate homes.

In addition to natural challenges, since the 1950s nitrogen loading has caused eelgrass to disappear in many locations. In Chesapeake Bay there is an effort underway to actively replant eelgrass rather than waiting for it to recover naturally.

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Traditional vs. conservation moorings

On Martha’s Vineyard the National Oceanic and Atmospheric Administration (NOAA) is teaming up with the Town of Tisbury to finance the introduction of “conservation moorings.” The chains on traditional moorings are replaced by floating plastic tubes that do not scour the bottom. The town has also passed a local law that requires property owners in the watersheds of Lake Tashmoo and the Lagoon Pond to install advanced septic systems that cut down on the amount of nitrogen leaching from the adjacent substrate into the nearby estuaries.

Once eelgrass is lost in an area, it is difficult to reestablish it if there is regular boat activity and if the surface water is regularly made turbulent by wind and tidal currents. All this energy causes the resuspension of fine bottom sediments that are no longer held in place by the eelgrass roots (and the water is no longer calmed by the dense eelgrass foliage). The suspended sediment shades the bottom and makes it difficult for eelgrass to grow.

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The Tender Heath

The climate of Martha’s Vineyard is mild and moist. The mildness is reflected in its assignment to USDA Hardiness Zone 7a, which means that temperatures do not descend below 0 to 5 degrees F in the winter. This is the same zone as Philadelphia and Nashville. The Vineyard is also humid; it is an island surrounded by the relatively cold water of the continental shelf. As the island warms relative to the surrounding ocean, the air cannot help but be drawn in over the land, bathing it with moisture evaporated from the sea. It is a miniature version of the Pacific Northwest, where the prevailing westerlies rise up first the coastal range and then the higher Cascades, cooling as they rise and dropping their moisture as rain and a fine mist. The forests of the Oregon coast and the forest of Martha’s Vineyard are both hung with fruticose lichens.

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Huckleberries, the red leaved shrub here, are an indicator of a heath community.

The interior of the island is droughty though. It is mostly sand (or a sandy loam) and water that falls quickly sinks into the substrate, out of reach of most crops. It was not settled in until the advent of drilled wells in the 20th century. Much of it was forested, but some of it was heath, which is a plant community dominated by woody shrubs and characteristic of sandy, over-drained areas. So-called anthropogenic heaths are those created and maintained by burning, grazing, or both.

As it happens Thomas Mayhew, the Englishman who bought Martha’s Vineyard in 1642 and settled it, was born in Tisbury in Wiltshire in south of England. The New Forest, which is in fact a patchwork of forest, heathland, and pasture, is in Wiltshire (and Hampshire), so the landscape of the island he settled may not have been as different from his homeland as we might think.

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Heather, an indicator of heathlands in the United Kingdom, in flower in Durham in the late summer.

To this day the New Forest is maintained in its patchwork condition by grazing. Blogger Stephen Bolwell describes the forest this way: “The look that is achieved with this approach to management isn’t exactly wild, but neither does it feel agricultural – it’s somewhere in between and usually happens in areas where the soil is too poor to support more intensive forms of agriculture.” Bolwell has been visiting the forest since the 1970s and has watched it decline due over-grazing by cattle and ponies. Plants like heather and bramble are now hard to find.

Once a grassland has replaced a heathland it is a precarious balance. Over-grazing can deplete even the grass leaving exposed sand, which elevates the temperature locally, causing a mesoclimate that makes the vegetation around the sand die and the desertification spreads. Heathlands are threatened in Massachusetts too. Here the threat is grazing, but also fire suppression and fragmentation by development.

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A statue of the heath hen by Todd McGrain looks out over the Martha’s Vineyard heath dominated by sheep laurel.

Because the heath is a marginal environment — prone to drought and wide swings in temperature — many plant and animal species are found there and not elsewhere (or are much more rare elsewhere). Bearberry (Arctostaphylos uva-ursi) and black huckleberry (Gaylussacia baccata) are indicator species for sandplain heathlands. Sandplain heathlands and sandplain grasslands share about 70 percent of their dominant species: it is the proportion of the species and the resultant structure that separates the types. Sandplain heathlands look shrubby and appear taller and have fewer vascular plant species than do grasslands. Heathlands are structurally similar to maritime dune communities in that each has low shrub, herbaceous and grassy growth with patches of bare soil.

Martha’s Vineyard was the last hold-out of the heath hen, an eastern population of the greater prairie chicken. It was in part the failure to maintain the actual heathlands that led to its extinction in 1932. The Heath Hen Preserve was established in 1908 and a population that had declined to 70 at the end of the 19th century recovered to 2000 birds by the mid 1910s. But the management of the preserve included fire suppression. Not only did this along the open grassland to succeed to scrub, but when fires did occur, they were dangerous. A 1916 conflagration precipitated the final decline of the species.

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Short and Spreading Oak

Nearly anywhere you go in the United States you will find oak trees. They are often large and common, so they can often contribute significantly to the look and feel of a place. The effect reaches consciousness if you are a plant nerd. During the year I lived on the Central Coast of California, I was somewhat distracted by the fact that several species of oak did not lose their leaves in the winter. And what could be more different than the spreading, moss-draped live oaks of the Southeast versus the upright, austere red and black oaks of the Northeast?

Spreading post oak in Texas

Spreading post oak in Texas

I have been reading that before the European settlement period Martha’s Vineyard was not as heavily dominated by oak forest as it is now. (When I repeated this statement to a naturalist in the employee of The Nature Conservancy, she contested it. And David Foster’s book A Meeting of Land and Sea indicates that it is a lot more complicated than that.) Supposedly, the up-island portion of Martha’s Vineyard, which is higher, rockier, and less sandy than down-island, was once more of a northern hardwoods assemblage, characterized by beech, maple (mostly red), black tupelo (locally called beetlebung).

But clearing of the forests for sheep raising between the 17th and 19th centuries led to erosion of organic-rich top soil, so when animal husbandry and farming faded and the island became a site for second homes, the forest that returned was one more adapted to drier sites with more mineral-dominated soils. In the Northeast, this tends to be the preferred habitat of the post oak (Quercus stellata).

I am not familiar with this species. It is a common oak in the South and southern Midwest, but is confined to marginal areas in the Northeast: sand barrens and rocky ledges. In Massachusetts it is found in Bristol and Barnstable counties on the mainland (Buzzards Bay and Cape Cod) and on the Islands. This represents the northeastern corner of its range; it extends southward along the Connecticut coast and on Long Island.

"Maltese cross" shape of the post oak leaf

“Maltese cross” shape of the post oak leaf

It is a famously slow-growing species and the wood is rot-resistant. It gets its common name from its sturdiness as a component of fence construction. It often takes a spreading form, the branches assuming sinuous shapes, and generally reaches the height of 50 feet, although it can grow to twice that height in a suitable location.

It is in the white oak group, so the lobes of the leaves are rounded and without the terminal ‘pins’. The acorns mature in one year and are sweet tasting. White oaks also readily hybridize among species, making identifying characters somewhat variable from tree to tree. The post oak usually has leaves that are said to resemble a Maltese cross; they are narrow at the base and have three broad, squared off lobes at the distal end. The underside of the leaves are covered with fine hairs called trichomes. In the post oak these have a star-shaped cross-section, hence the trivial name stellata.

Allen's Farm, Martha's Vineyard

Allen’s Farm, Martha’s Vineyard

Oak leaves are poisonous to sheep and goats, so it seems odd that they are so common on this island, where sheep raising was such an important part of the economy. Apparently the sheep won’t each the leaves if there is enough grass around. Sheep are consummate grazers, even less likely to browse than cattle or horses.

When you wander the conservation lands of Martha’s Vineyard, you frequently encounter stone walls that now wend their way through the woods, but once delimited the boundaries of sheep meadows. Amid the younger trees you find larger, spreading trees — they are occasionally post oaks — that must have been there to provide shade for sheep and shepherd. I still have some questions about whether eating oak leaves was a concern, but it is a pleasant picture to conjure.

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